Process of effecting thermochemical reactions



Patented June 1, 1926.

UNITED STATES PATENT OFFICE.

CHARLES B. JACOBS, OF WILMINGTON, DELAWARE, ASSIGNOR TO E. I, DU PON'IDE NEMOUBS 6'0 COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELA-WARE.

PROCESS OF EFFECTING THERMOCHEMIGAL REACTIONS.

No Drawing. Application filed November 27, 1929. Serial No. 426,863.

droxide, and carbon obtained as a by-prodnot in cellulose purification,with or Without a reducible compound of a carbide or nitrideformingmetal such as iron, to a temperature sufficient to efiect a reactionbetween the carbon, the nitrogen and the alkali-metal carbonate orhydroxide, to form an alkali-metal cyanide. Typical examples of theprocess of making alkali-metal cyanides involving the application ofthis highly reactive carbon were cited-awith sodium chloride or sodiumfluoride as the chief accelerating agent present, and also with ironoxide used in conjunction with sodium chloride or sodium fluoride as theaccelerating agents. These examples showed that the substitution of anequal Weight of this highly reactive carbon for the ordinary carbonpreviously used, resulted in the conversion to sodium cyanide of from 95to 98% of the sodium carbonate present in the charge in approximatelyonehalf the time required to convert 75 to 85% of the sodium carbonateto sodium cyanide when the ordinary form of carbon was used, theoperations being carried out under otherwise identical conditions.

In the ordinary process f recovering the soda compounds from paper pulpmill black liquor, this liquor, after evaporation to about 35 B., is fedinto incinerators, usually of the rotary type, where at the expense of apart of the contained carbon, the water is evaporated and a black ashresults containing substantially 85-90% sodium carbonate and 1510%carbon, the mass in the incinerator becoming heated to a red heat, thatis to a temperature above 550 (1, during the operation. I have fou ndupon further investigation that if, instead of incinerating the blackliquor by this usual method, Whereb the residue becomes heated to such abig temperature, it be evaporated to dryness at comparatively lowtemperatures, i. e. below a red heat and preferably at about 200300 0.,there results the usual recovery of soda ash with an increased yield ofcarbon. The linal residue contains sodium compounds equivalent to -65%soda ash, and 0-35% carbon. The carbon, when obtained in this condition,is much more active than that oh- This invention relates to processesinvolving thermo-chemical reactions in which the element carbon is anactive constituent of the reacting materials by virtue of its power tocombine with the other reacting elements to form either volatile ornon-volatile chemical compounds. The invention pertains especially toprocesses of the above character in which it is essential that thecarbon constituent of the reacting materials be particularly adapted forthe process reactions by reason of its purity and chemical activity.

In my pending application, Serial No. 309,920, filed July 10, 1919,process effecting chemical reactions with by-product carbon fromcellulose purification, I described the activity of carbon obtainedthrough the incineration of the black liquor resulting from treatment ofvarious fibers for the purification of their contained cellulose. I alsodescribed the method of obtaining this black liquor by the cooltinp ofwood, straw, or various similar fibers with caustic soda solutions inthe production of pulp for the manufacture of paper. I outlined theusual method of incinerating black liquor in rotary furnaces where, atthe expense of a part of the contained carbon, the Water is evaporatedand a black ash results containing substantially 85') to 90% of sodiumcarbonate and 15 to 10% of carbon.

In my previous application mentioned above. I stated that the discoveryof this form of carbon constituted a dcsidt-u'atum for theroic-chemicalreactions which involve carbon as a reactive element. I gave examples ofthe application of this form of carhon to thermo-chemical reactions andspecifically related its application in the produc' tion of alkali-metalcyanides as described in my applications Serial No. 279,801 and SerialNo. 279.802. filed February l9l9. the following equation expressing thegenerally accepted reaction involved:

This process of producing ulkalim'ietul ryanidcs, stated generically,comprises heating in coniaet with nitrogen a mixture containing analkali metal halide. a compound tained by incineration at the highertemperaof an alkali-metal other than a halide. as for ture, and thus, inaddition to obtaining the example an alkalianetal carbonate or hy sameamount of soda ash for return to the for use in thermo-chemicalreactions in genera], and for use as a catalyzer for promoting gasreactions, and as a decolorizing agent. These latter uses, as well asthe use of this carbon in the thermo-chemical reaction involving theproduction of metallic sodium,

are fully described and claimed in my copending application, (Case 0)Serial No. 426,864, filed coincidently with this.

The new carbon produced in the above described manner, either before orafter removal of soda ash, may be referred to as carbon obtainable by termally decomposing the alkali-soluble constituents of wood at atemperature below 550 (3., and by this expression I mean to includecarbon derived in like manner from cotton, esparto, straw, andequivalent vegetable fibers.

The organic constituents of wood which are dissolved by the alkali usedin the soda process, include certain forms of cellulose which aresoluble in sodium hydroxide solution, and various resins. The proportionof cellulose soluble in sodium hydroxide solution, and of resins, variesconsiderably in different kinds of wood. The sodium hydroxide-solublecellulose is usually present in substantial proportions; the carbonobtained from wood in the abovedescribed manner may therefore be said toconsist essentially of alkali-soluble-cellulose carbon andalkali-soluble-wood-resin carbon. The alkali-soluble form (i. e. thebeta and gamma forms) of cellulose, also exists to some extent incellulosic substances such as cotton, esparto, straw, etc; the carbonobtained from the alkali-soluble constituents of wood and other crudecellulose of this kind may be referred to generically asalkalisoluble-cellulose carbon.

On account of the extreme affinity of this form of carbon for oxygen(even at comparatively low temperatures, as fully described in thecopending application mentioned above), it is desirable in evaporatingthe black liquor to carry out the operation in the absence of air, i. e.in closed pans or pots, and to cool the resultant mixture of carbon andsodium compounds to below 80 C., and

the charge is to contain other constituents or other proportions of sodaash and carbon, the evaporated residue may be used as the basis forbuilding up the charge; as for instance, in the production ofalkali-metal cyanides in accordance with my pending applications, SerialNo. 279,801, filed February 28th, 1919, and also Serial No. 279,802,filed on the same date. In these particular cases, it is, however,unnecessary to evaporate the black liquor to dryness before adding theother constituents of the charge.

Paper pulp mill'black liquor, as it is usually produced andevaporated'to a concentration of about 35 B., preparatory to the usualmethod of incineration, contains approximately 56% water and about 44%potential soda ash and carbon, the latter percentage in the proportionsof about 6065 parts of soda ash to 4035 parts of carbon. In constructingthe preferred chargefor the production of alkali-metal cyanides inaccordance with the above-mentioned specifieations,for example, asdescribed in application Serial No. 279,802, where iron oxide andalkali-metal halides are used in conjunction as the accelerating agentsor catalyzers in the production of alkali-metal cyanide,-it is onlynecessary to add to this black liquor the necessary catalyzers, and toevaporate the whole mass to dryness preferably with exclusion of air attemperatures below 550 C. (for example about 300 C). Thus, for example,a charge composed of 440 lbs. of black liquor (at 35 B., the usualstrength), 50 lbs. of oxide of iron, and 5 lbs. of sodium fluoride,yields on evaporation under the above conditions, a furnace charge ofsubstantially the following composition:

Per cent. Sodium carbonate 46 By-product carbon 37 Iron oxide 20 Sodiumfluoride 2 The charge made up as above described is placed in a suitableretort, connected with a nitrogen supply, and subjected to a temperatureof from 900 to 950 (1., preferably under a nitrogen pressure of about 23to 30 lbs. absolute. There results a furnace product having a sodiumcyanide content of about 5055%, which is equivalent to a conversion tosodium cyanide of about 95 to 98% of the sodium carbonate present, ascompared with a sodium cyanide content of about 40-45% when carbonobtained by incineration of the black liquor at a red hbat is used inplace of the carbon obtained by evaporation of the black liquor at lowtemperatures. The higher result is, moreover, obtained in about 30% lesstime than is required when carbon obtained by incineration of blackliquor at higher temperatures is used in the making up of the charge.

The 10% higher sodium cyanide content in the furnace product may beexplained as follows: When using this more chemically active form ofcarbon obtained by the decomposition of black liquor at lowtemperatures, it is possible to carry a higher proportion of sodiumcarbonate in the furnace charge for the production of alkali metalcyanldes than w on using the old form of carbon. When using the carbonobtained by the ordinary method of incinerating black liquor at highertemperatures, the maximum amount of sodium carbonate it is advisable tocarr in the furnace charge is about 40% of t e weight of the charge,while in the example cited above 46% of the weight of the charge wascomposed of sodium carbonate. Since, substantially the same conversionof sodium carbonate to sodium cyanide was obtained with the 46% chargein 30% less furnacing time than was required by the 40% charge, theweight of cyanide produced per furnace hour and per pound of chargefurnaced was very materially increased.

To illustrate how the proportions of several ingredients may be varied,the following example is given of the composition of the furnace charge:

Parts. Sodium carbonate 46 Carbon (reactive) 35to45 Alkali-metal halide1 to 10 Iron oxide 35to15 Although the carbons described in my copending applications Ser. No. 309920 and 312610 and in the present caseare both highly reactive, the latter may be distinguished from theformer by the lower temperature at which carbonization is effected, andby the lower ignition temperature in air of the new carbon, thistemperature for the majorit of samples being below 0., whereas t eignition temperature of the carbon described in the above mentionedapplications is as a rule above 90 C.

The advantages and improvements in the art attained by the substitutionofthis particular form of carbon, and consisting in material increase inyield and distinct shortening of the time required for the completion ofthe reaction, will be readily appreciated by those familiar with theart. Further, I have found the application of this form of carbon tothermo-chemical operations diflering in many ways from those mentionedabove, to be advantageous. Thus, I may form it into briquettes withvarious other materials to carry out various thermochemical reactions;or I may make compositions of it with various inert materials to obtainan extended reaction surface of carbon for use as a catalyzer, as forexample,

in the manufacture of phosgene; or I may use it as a decolorizing agent;or I may employ it to carry out thermochemical reactions in which ses,vapors, or liquids are required to be rou ht into contact with largesurface areas of c emically active car- Usually this reaction does nottake place to any extent except at quite elevated temperatures (in theregion of 10501150 C.) and rapidly only at still higher temperatures.The extreme activity of the carbon obtained from black liquor evaporatedto dryness at low temperatures, and its very intimate contact with thesodium salts present with it during the evaporation, permits thisreaction to take place'at unusually low temperatures, thus making itpossible to carry out the operationof the production of metallic sodiumfrom sodium compounds by direct reduction with carbon, without unduedeterioration of the retorts. It is well known to those versed in theart that the direct reduction of sodium compounds by carbon has not beensuccessful commercially on account of the extremely high temperaturerequired, and the consequent wear and tear on the apparatus.

I claim 1. The process of decomposing an oxygencontaining metal compoundwhich comprises subjecting to a high temperature a mixture containingsaid metal compound and alkalisoluble-cellulose carbon having anignition temperature below 90 C. in am 2. The process of decomposing anoxygencontaining metal compound which comprises subjecting to a hightemperature with exclusion of gaseous oxygen a mixture containing saidmetal compound and alkalisoluble-cellulose carbon having an ignitiontemperature below 90 C. in air.

3. The process of separating oxygen from a substance containingchemically bound oxygen which comprises heating said substance to a hightemperature in contact with alkali-soluble-cellulose carbon having anignition temperature below 90 C. in air.

4. The process of separating oxygen from be cited in the use of thepotential a substance containing chemically bound oxygen which comprisesheating said substance to a high temperature in contact with carbonobtainable by thermally decomposing the alkali-soluble constituents ofwood at a temperature below 550 C.

5. The process of effecting reactions between a substance whose moleculecontains oxygen and a substance whose molecule does not contain oxygenwhich comprises bringing said substance in contact with highly heatedalkali-soluble-cellulose carbon having an ignition temperature below 90C. in air.

6. The process of effecting reactions between nitrogen and anoxygen-containing compound of an alkali-forming metal which comprisesbringing nitrogen in contact with a mixture comprising saidoxygen-containing alkali-forming metal compound andalkali-soluble-cellulose carbon having an ignition temperature below 90C. while maintaining said mixture at a high temperature.

7. lhe process of effecting reactions be tween nitrogen and anoxygen-containing compound of an alkali-forming metal which comprisesbringing nitrogen in contact with a mixture comprising said oxygencontaining alkali-forming metal compound, an alkali-metal halide, andalkali-soluble-cellulose carbon having an ignition temperature below 90(i. while maintaining said mixture at a high temperature.

8. The process of effecting reactions between nitrogen and analkali-metal carbonate which comprises bringing nitrogen in contact witha mixture comprising said alkali metal carbonate, an alkali-metalhalide, and alkali-soluble-cellulose carbon having an ignitiontemperature beow 00 C. while maintaining said mixture at a hightemperature.

0. The process of cftecting reactions between nitrogen and analkali-metal carbonate which comprises bringing nitrogen in con tactwith a mixture comprising said alkalimetal carbonate, an alkali-metalhalide, and carbon obtainable by thermally decomposing at a temperaturebelow 550 C. the alkali-soluble constituents of Wood, while maintainingsaid mixture at a high tempera- 'ture.

10. The process of effecting reactions between nitrogen and anoxygen-containing compound of an alkali-forming metal which comprisesbriging nitrogen in contact with a mixture comprising said oxygencontaining alkali-forming metal compound, a finely divided substancecomprising iron. an alkalimetal halide, and alkali-solublecellulosecarbon having an ignition temperature below 90 C. while maintaining saidmixture at a high temperature.

11. The process of producing an alkalimetal cyanide which comprisesheating in contact with nitrogen a nnxture containing an alkali-metalhalide, a reducible compound of a carbide-forming metal, a compound ofan alkali-metal other than a halide, and alkali-soluble-cellulose carbonhaving an ignition temperature below 90 C., to a temperature sufficientto effect a reaction between the carbon, nitrogen, and the last men--tioned alkali-metal compound to form an alkali-metal cyanide.

12. The process of making sodium cyanide which comprises heating incontact with. nitrogen a mixture containing a sodium halide, iron oxide,sodium carbonate, and alkali-soloble-cellulose carbon having an ignitiontemperature below 90 (3., to a temperature suflicient to effect areaction between the carbon, nitrogen, and the sodium carbonate to formsodium cyanide.

13. The rocess of producing an alkalimetal cyanide which comprisesheating in contact with nitrogen a mixture containing an alkali-metalhalide, a reducible compound of a carbide-forming metal, a. compound ofan alkali-metal other than a halide, and carbon obtainable by thermallydecomposing at a temperature below 550 C. the alkalisoluble constituentsof wood, to a temperature sufticient to effect a reaction between thecarbon, nitrogen, and the last mentioned alkali-metal compound to forman alkalimetal cyanide.

14. The process of making sodium cyanide, which comprises heating incontactwith a nitrogenbearing gas a. mixture containing sodium fluoride,a reducible compound of a carbide-forn'iing metal, sodium carbonate, andcarbon obtainable by thermall y decomposing at a temperature between 200and 350 C. the alkali-soluble constituents of wood, to a temperaturesufiicient to effect a reaction between the nitrogen, carbon and sodiumcarbonate to form sodium cyanide.

15. The process of making an alkali-metal cyanide, which comprisesheating in contact with a nitrogen-bearing gas a mixture containing analkali-metal halide, a finely divided substance comprising iron, acompound of an alkal -metal other than a halide, and carbon obtainableby thermally decomposing at a temperature between 200 and 350 C. thealkali-soluble constituents of wood, to a temperature sufiicient toeffect a reaction between the carbon, nitrogen and the alkali-metalcompound to form an alkalimetal cyanide.

16. The process of making an alkali-metal cyanide, which comprisesmaking a mixture containing an alkali-metal halide, a reducible compoundof a carbide-forming metal, a compound of an alkali-metal other than ahalide, and carbon obtainable by thermally decomposing at a temperaturebelow 550 C. the alkali-soluble constituents of wood, heating themixture in a closed retort promamas vided with an exit for the escape ofgaseous 17. The rocess of making an alkali-metal cyanide, w ichcomprises making a mixture of an alkali-metal halide, oxide of iron, :1.com und of an alkali-metal other than a hali e, and carbon obtainable bythermally decomposing at a temperature between 200 and 350 C. thealkali-soluble constituents of wood, heatin the mixture ina closedretort provided with an exit for the escape of gaseous products to asuflicient temperature to expel gaseous reduction products from theoxide of iron to render the mixture porous, and subjecting the porousmixture to the action of a nitrogen-bearing gas, at a temperaturesuificient to effect a reaction between the carbon, nitrogen and thealkali-metal compound to form an alkali-metal cyanide.

18. The rocess of making an alkali-metal cyanide, w ich com rises makinga mixture of an alkali-metal iialide, a reducible compound of acarbide-forming metal, a compound of an alkali-metal other than ahalide, and carbon obtainable by thermally decomposing at a temperaturebelow 550 C. the alkali-soluble constituents of wood, heating themixture in a closed retort provided with an exit for the escape ofgaseous products to a temperature of from about 850 to 950 (1., andsubjecting the heated mixture to the action of nitrogen, substantiallyas described.

19. The rocess of making an alkali-metal cyanide, w ich comprisespassing nitrogen gas under an absolute pressure of from about 23 to 35ounds per square inch in contact with a mlxture containing analkalimetal halide, a reducible compound of a carbideforming metal, acompound of an alkali-metal other than a halide, and carbon obtainable bthermally decomposing at a temperature below 550 C. the alkali-solubleconstituents of wood, while maintaining said mixture at a temperaturesufficient to effect a reaction between the carbon, nitrogen andalkali-metal compound to form an alkalimetal cyanide.

20. The process of making a sodium cyanide which comprises heating incontact with.

nitrogen a mixture containing from 1 to 10 parts of an alkali-metalhalide, from 35 to 15 parts of iron oxide, about 46 parts of sodiumcarbonate and from to 45 parts of carbon obtainable by thermallydecomposing at a temperature below 550 C. the alkali-solubleconstituents of wood, to a temperature suiiicieutto effect a reactionbetween the carbon, nitrogen and the sodium carbonate to form sodiumcyanide.

21. The process of effecting reactions be 'tween nitrogen and analkali-metal carbonate which comprises heatin a mixture containingalkali-soluble cellu ose, and alkalimetal compound, water, and ironoxide to a temperature below 550 C. but high enough to evaporate thewater and to carbonize the cellulose, and then bringing nitrogen incontact with the resulting mass at i a high temperature.

22. The process of effecting reactions between nitrogen and analkali-metal carbonate which comprises heating a mixture containingalkali-soluble cellulose, an alkali-metal compound, water and iron oxideto a temperature below 550 C. but high enough to evaporate the water andto carbonize the cellulose, and then bringing nitrogen under pressure incontact with the resulting mass at a temperature of from about 850 to950 C.

23. The process of eiiecting reactions between nitrogen and sodiumcarbonate which comprises heating with exclusion of air a mixturecontaining alkali-soluble cellulose, a. sodium compound, water, and ironoxide to a temperature below 550 C. but high enough to evaporate thewater and to carbonize the cellulose, and then bringing nitrogen incontact with the resulting mass at a 1gb temperature.

24. The process of effecting reactions between nitrogen and sodiumcarbonate which comprises heating with exclusion of air a mixturecontaining alkali-soluble cellulose, a sodium compound, water, and ironoxide to a temperature below 550 C. but high enough to evaporate thewater and to carbonize the cellulose, and then bringing nitrogen incontact with th"resulting mass at a temperature of from about 850 to 950C.

25. The rocess of producing an alkalimetal cyanlde which comprisesincorporatating iron oxide in soda pulp black liquor, evaporating themixtureto dryness, and then subjecting it to the action of nitrogen at ahigh temperature.

26. The process of producing an alkalimetal cyanide which comprisesincorporating iron oxide in soda pulp black liquor, evaporating themixture to dryness at a temperature between 200 and 550 C. whileexcluding air therefrom, and then subject ing the dry mass at atemperature of from about 850 to 950 C. to the action of nitrogen.

27. The process of producing an alkalimetal cyanide which comprisesincorporating a reducible compound of a carbideforming metal in sodapulp black liquor, evaporating the mixture to dryness at a. temperaturebetween 200 and 550 C. while excluding air therefrom, and then subject.-

ing the dry massat a temperature of from about 850 to 950 C. to theaction of nitroen. g 28.'The recess of producing an alkalimetal cyanidewhich comprises incorporating a reducible compound of a carbideforniingmetal and an alkali-metal halide in soda pulp black liquor, evaporatingthe mixture to dryness at a temperature between 200 and 550 C. whileexcluding air therefrom, and then subjecting the dry mass at atemperature of from about 850 to 950 C. to the action of nitrogen.

29.'The process of producing an alkalimetal cgizmde which comprisesincorporat ing a ely divided substance comprising iron and analkali-metal halide in soda pulp black liquor, evaporating the mixtureto dryness at a temperature between 200 and 550 C. while excluding airtherefrom, and then subjecting the dry mass at a temperature of fromabout 850 to 950 C. to the action of nitrogen.

In testimony whereof I aflix my signature.

CHARLES B. JACOBS.

29. The process of producing an alkalimetel cfiygmide which comprisesincorporating a ely divided substance comprising iron and analkali-metal halide in soda pulp black liquor, evaporating the mixtureto dryness at a temperature between 200 and 550 C. while excluding airtherefrom, and then subjectin the dry mass at a temperature of from aout 850 to 950 C. to the action of nitrogen.

In testimony whereof I aflix my signature.

CHARLES B. JACOBS.

CERTIFICATE OF CORRECTION.

Patent No. g l, 587, 323.

June 1, 1926.

CHARLES B. JACOBS.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: In theheading to rinted specification, line 5, date of filing, for "November27, 1929" the read "November 27, 1920"; and that the said Letters Patentshould be read with this correction therein that the same may conform tothe record of the case in the Patent Office.

Signed and sealed this 16th day of May, A. D. 1933.

(Seal) I M. J. Moore.

Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

. Patent No. 1,587,323. June 1, 1926.

CHARLES B. JACOBS.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: In theheading to the printed specification, line 5, date of filing, for"November 27, 1929" read "November 27, 1920"; and that the said LettersPatent should be read with this correction therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed this [6th day of May, A. D. 1933.

M. J. Moore. (Seal) Acting Commissioner of Patents.

